Isolation and sequence determination of an immunodominant antigen from Enterococcus faecalis

Abstract

Immunoblotting serum from patients with endocarditis due to Enterococcus faecalis has previously identified three antigenic bands of 112, 88–90 and 45–47 kDa which were demonstrated as being endocarditis specific. We have isolated a partial DNA clone for the highly immunogenic 88–90 kDa antigen of E. faecalis. The lambda ft11 libarary was screened with pooled sera from patients with E. faecalis endocarditis, and a positive clone for the 88–90 kda band identified by affinity-purified antibody probes. The continuous open reading frame of 1932 nucleotide encoded for a predicted polypeptide of 644 amino acids with a molecular weight of 72541 daltons. Homology sequence analysis indicated the presence of a putative internal repeat bearing consensus nucleotide binding motifs. We believe this is the first reported gram-positive bacterial ATP-binding protein that contains two ATP-binding domains within a single protein.